The relationship between cement properties and drying shrinkage of partially hydrated neat cement pastes of normal consistency made of a large number of portland cements of different types and composition were studied by fitting multivariable regression equations with the aid of a digital computer. The time of cracking of annular specimens restrained from shrinking by a steel core varied from 0.1 to more than 40 hours. The principal variables which appeared to have the greatest effect were the fineness and K2O and C4AF contents of the cements. The fineness and K2O contents of the cements appeared to have the greatest effect on the nonrestrained shrinkage of prisms at the time of cracking of the annular specimens. The shrinkage of neat cement bars after 1, 6, 27 days, and 6 months in laboratory air differed greatly with different cements. The principal variables appeared to be the C3A, SO3, and C3A/SO3 ratios. Other commonly determined variables were associated with each of the above test values. The trace elements, other than Na20 and K2O, were not generally associated with the shrinkage or cracking characteristics. Keywords: Chemical composition of portland cements; cracking of portland cements; cracking resistance of cements; portland cement; shrinkage of Portland cements; trace elements. Page 1. * Included among those notations etc. are the use of C3A, C3S, CzS, and C4AF for the calculated potential compound composition of the cements, viz, tricalcium aluminate, tricalcium silicate, diealcium silicate and tetraealcium aluminof errite. Also used are Loss for loss on ignition, Insol for insoluble residue, and APF for airpermeability fineness. Also used are AE + NAE to designate airentraining plus non-air-entraining cements and NAE for the nonair-entraining cements. The compressive strength in psi of 1:2.75 (cement to sand) mortars cured for 1, 3, 7, 28 days, and 1 year are designated by STOl, ST03, ST07, ST28, and STIY respectively. * Note (1) Ratio of number of plotted points in pairs of diametrically opposite quadrants. Note (2) General trend of lines drawn through plotted points. Note (3) Apparent nature of relationship. L = linear; NL =: nonlinear; NO = no apparent relationship; and L? = nature of relationship not determinable. (Note (4) Quadrant sum in corner test (see reference 5). * Note (1) Ratio of number of plotted points in pairs of diametrically opposite quadrants. Note (2) General trend of lines drawn through plotted points. Note (3) Apparent nature of relationship. L = linear: NL = nonlinear; NO = no apparent relationship; and L? = nature of relar tionship not determinable. Note (4) Quadrant sum in corner test (see reference 5).

Seve ntee n brands of masonry cement were tested fo r so un d ness, stre ngth , consistency, fi ne ness, tim e of setting, shrinkage, water re pe ll ency, wate r r ete nt io n, autocla,·c cx pa nsion, air ent rainm ent, and resistance to freezin g and t hawin g. \1 0rta rs were pro po rti o ned both by weight and by volum e. Au toc lave tests indi cated po te nt ia l unsoundness in so m c of t he cem ents. Air e ntrained in t h e mort ar \\"as effective in in creasing t he abilit y to withst a nd freezin g and t h awing. The shrinkage of t h ese ce me nts differed g reat ly. The r es ults of tests indicated a lso t hat t he propert ies of t hese m aso nry ce ments ,,·ere ap preciab ly diffcrent from those prcv ious ly re ported in 1934.

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